1. Field of the Invention
The present invention relates to an image forming apparatus, which employs an electrophotographic method, such as a laser printer, a copying machine, and a facsimile machine.
2. Description of the Related Art
A color image forming apparatus, in which a plurality of photosensitive drums for forming an image are disposed, forms the image by sequentially transforming toner images formed on the photosensitive drums onto an intermediate transfer belt disposed facing the plurality of photosensitive drums respectively or a transfer member conveyed by a conveyance belt.
Adhering substances such as toner that is not transferred to the transfer member and paper powder may adhere to the intermediate transfer belt or the conveyance belt used in the image forming apparatus described above, and thus a cleaning unit for removing the adhering substances from the belt is provided therein. As the cleaning unit, a method is conventionally known for removing the toner by causing an elastic cleaning blade to contact the belt.
However, in the image forming apparatus that employs the cleaning blade, a friction force is increased at an abutment portion of the cleaning blade and the belt, and thus the adhering substances may not be removed from the belt by the cleaning blade. To solve such a problem, Japanese Patent Application Laid-Open No. 2004-125900 discusses a toner supply control method, in which the toner images are formed on the belt at timings other than image formation, and then the formed toner images are supplied to the abutment portion of the cleaning blade and the belt.
The toner supply control method discussed in Japanese Patent Application Laid-Open No. 2004-125900 periodically supplies the toner to an edge portion of the cleaning blade, so that the friction force generated between the cleaning blade and the intermediate transfer member can be reduced.
However, the timing for performing the toner supply control as discussed in Japanese Patent Application Laid-Open No. 2004-125900 is determined by a printing ratio, with which the toner supply control may be unnecessarily performed to excessively consume the toner.
For example, in an environment of high temperature and high humidity, the friction force generated between the belt and the cleaning blade is hardly increased, and thus even if the toner is not supplied to the abutment portion of the cleaning blade and the belt, the adhering substances may be removed from the belt by the cleaning blade. However, the technique discussed in Japanese Patent Application Laid-Open No. 2004-125900 has a problem in which, since the toner supply control is performed even in the environment of the high temperature and the high humidity with a predetermined timing, the toner is consumed uselessly.